This invention relates to phased array antenna data processing and, in particular, to a method and apparatus for digital phased array antenna data alignment.
Phased array antenna systems generally employ fixed, planar arrays of individual, or subarrays of, transmit and receive elements. Phased array antennas receive signals at the individual elements and coherently reassemble the signals over the entire array by compensating for the relative phases and time delays between the elements. For transmission, the relative phase compensation is applied to the signals at each of the individual elements to electronically steer the beam.
In conventional phased array antennas, the phase shifts and time delays are applied in the analog domain. Typically, the received signals are combined across an array using analog microwave combining circuits and down-converted to an intermediate frequency using analog microwave mixer components. The intermediate frequency is further processed in the analog domain prior to digitization at a low baseband frequency. This analog processing approach is generally not applicable to large arrays, since wide-bandwidth signals do not retain phase coherency over large arrays. Wideband signal processing in large phased arrays requires programmable true-time-delay components to combine the wideband signals over the array. Programmable, analog, true time delays are generally large, complex and costly components.
To help solve this problem for wideband signals, digital processing of the antenna signals has been attempted. This process typically involves digitally processing the received signals at an intermediate frequency. This digital solution requires high precision, high speed, analog-to-digital converters with large power demands to digitize the intermediate frequency.
In accordance with the present invention, the disadvantages and problems associated with previous phased array antennas have been substantially reduced.
In particular, the present invention provides a method and apparatus for digital phased array antenna data processing. The digital phase array antenna comprises a plurality of antenna elements, each element operable to receive a signal. An analog-to-digital converter is coupled through RF amplification and matching circuitry to at least one of the antenna elements to convert the signal to a multi-bit digital signal. Also included is a data re-alignment circuit coupled to the analog-to-digital converter to correct the received data for angle of arrival.
In another embodiment, there is provided a method for time re-aligning data received at a digital phase array antenna. This method includes the step of receiving a radar signal at an antenna element. Next, the signal is converted to a multi-bit digital signal using an analog-to-digital converter. Finally, the alignment of the multi-bit signal is corrected by applying a master clock to the analog-to-digital converter and applying time delays in the digital domain.